Imaging member and method

ABSTRACT

An imaging member comprising a donor sheet and an imaging layer coated thereon wherein the donor sheet comprises an electret. The imaging member is employed in the manifold imaging process wherein the imaging layer is subjected to an electric field which field is supplied by the electret. While subjected to the electric field the imaging layer is exposed to electromagnetic radiation to which it is sensitive and fractured in imagewise configuration in the manifold imaging mode.

[111 3,850,626 [451 5 Nov. 26, 1974 IMAGING MEMBER AND METHOD [75]Inventor: Ray II. Luebbe, Jr., Rochester, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: Feb. 26, 1973 21 Appl. No.: 335,982

[52] US. Cl. 96/1 M, 96/l.5

OTHER PUBLICATIONS Fridkin, Photoelectrets and the ElectrophotographicProcess pp. 1-3 174, 175.

Primary Examiner.-David Klein 7 Assistant Examiner.lohn L. Goodrow [5 7]ABSTRACT An imaging member comprising a donor sheet and an imaging layercoated thereon wherein the donor sheet comprises an electret. Theimaging member isemployed in the manifold imaging process wherein theimaging layer is subjected to an electric field which field is suppliedby the electret. While subjected to the electric field the imaging layeris exposed to electromagnetic radiation to which it is sensitive andfractured in imagewise configuration in the manifold imaging mode.

18 Claims, 6 Drawing Figures PATENTEL W 3,850,626

ACTIVATE FIG. 4/1

I SANDWICH APPLY FIELD AND EXPOSE 7 SEPARATE FIG. 4 A r16. 46

IMAGING MEMBER AND METHOD BACKGROUND OF THE INVENTION This inventionrelates in general to imaging and more particularly to layer transferimaging and improvements therein.

The manifold imaging system has been known as an imaging technique basedupon the transfer of an imaging layer comprising a cohesively weak orstructurally fracturable electrically photosensitive material sandwichedbetween a pair of'sheets. In the most common embodiment of this imagingtechnique a layer of electrically photosensitive imaging material isprovided residing on a substrate. This substrate is commonly called adonor sheet. In most cases the imaging layer comprises an electricallyphotosensitive material dispersed in a binder. An electric field isapplied across this imaging layer and the imaging layer is exposed to apattern of light and shadow representative of the image to bereproduced. With a receiver sheet in place over the im-.

aging layer and the electrical field extending across the sandwich, thedonor and receiver sheets are separated whereupon the imaging layerfractures along the lines defined by the pattern of light and shadow towhichthe imaging layer is exposed. Part of the imaging layer istransferred to one of the sheets while the remainder is retained on theother sheet so that a positive image, that is a duplicate of theoriginal is produced on one sheet while a negative image is produced onthe other. A more complete explanation of such an imaging process iscontained in U.S. Pat. No. 3,707,368 hereby'incorporated by reference.

Since the discovery of the manifold imaging process, the electric fieldacross the imaging layer during the exposure step and during theseparation of the sandwich has been, for the most part, described asbeing supplied by a pair of electrodes. The electric field can also besupplied by static electric charges on the surface of at least one orboth of electrically insulating donor and receiver sheets. Such amethodis further described in U.S. Pat. No. 3,6l5,393 to Krohn et al. insuch a process the manifold sandwich or at least one member such as thedonor sheet is electricallycharged such as by passing a member through apair of roller electrodes oremploying a corona discharge device such asthose ployed in order to transmit to the insulator sufficient staticcharges for usein the process, Further, the loss of the charges could beoccasioned by accidental grounding, humid atmospshere and materialswhich prove to be too conductiveto support such charges. There istherefore, a need for a more convenient method of placing an electricfield across an imaging layer in the manifold imaging process. Such amethod should eliminate the need for the presence of electrodes andprovide a field which can be more conveniently created, handled andutilized in the manifold process.

SUMMARY or THE INVENTION It is, therefore, an object of this inventionto provide a layer transfer imaging method having a convenientelectrical system.

Another object of this invention is to provide an imaging member for usein a layer transfer imaging method which member provides its'ownelectrical system.

Another object of this invention is to provide a layer transfer imagingmethod employing much lower voltages than previously possible.

of the donor sheet ln use, the novel imaging member of this inventionprovides an electric field across the imaging layer by employing'aconductive layer over each side of the manifold sandwich. The conductivelayers are placed in electrical commumication with each other in'suchmanner the electrical charge stored in the electret is-extended acrossthe imaging member rendering it useful in .the manifold imaging processwherein the electrically photosensitive imaging layer is exposed toelectromagnetic radiation and subsequently fractured by the separationof thereceiver and donor sheets.

Thus there is provided in accordance with this invention a manifoldimaging process wherein the electrical field across the imaging layerduring the exposure step and separation step is provided by theelectrical charges stored in a donor sheet which comprises an electret.

As in. the prior art of manifold imaging, the-term donor" is employedherein to describe the structure of an imaging layer coated on a donorsheet. There is also provided in accordance with this invention a novelimaging member for use in the manifold imaging method comprising anelectrically photosensitive layer which is or can be renderedstructurally fracturable in response to the combined effects ofexposure'to electromagnetic radiation to which it is sensitive and anapplied electrical field residing upon a donor sheet which donor sheetcomprises a electret. Such member can be employed in the manifoldimaging process such as by providing thin, transparent electricallyconductive coatings on the donor and receiver sheets as described above.Whilev scribed provides an imaging member having a thermosolvent incontact with the imaging layer. Upon heating the thermo-solvent layerabove its melting point the melted layer permeates the imaging layerthus activating it or, in other words, renders such layer structurallyfracturable in response to the combined effects of an applied electricfield and exposure to electromagnetic radiation to which the layer issensitive. Typical thermo-solvents are octadecane, nonadecane, eicosane,docosane and others as described in said patent. The thermo-solventlayer is commonly melted by contacting it with hot air, a heated rolleror other suitable heat transfer means.

DETAILED DESCRIPTION OF THE INVENTION The manifold imaging member andprocess are more clearly described with reference to the attacheddrawings wherein;

FIG. I is a side sectional view of the novel donor imaging member ofthis invention.

FIG. 2 is a side sectional view of the electrical configuration of theimaging member donor of this invention prior to its use in the manifoldimaging layer.

FIG. 3 is a side sectional view of the electrical configuration of thedonor of this invention while supplying the electrical field in themanifold imaging method.

FIG. 4 is a process flow diagram of the method steps of the manifoldimaging process of this invention.

FIGS. 4A and 4B are side sectional views diagrammatically illustratingthe process steps of this invention.

Referring now to FIG. 1 there is seen donor 10 comprising a supportingdonor sheet 11 which is an electret as indicated by the positive andnegative charges in said sheet and an imaging layer generally designatedas 12. Imaging layer 12 comprises, in this illustrative embodiment,photosensitive material 13 dispersed in an insulating binder 14. Alsoshown in FIG. I are conductive layers 15 and 15A which are open atswitch 16. With respect to the conductive layers 15 and 15A FIG. I isexpanded but in practice the conductive layers are placed in contactwith the surfaces of the donor. In the open condition the donor (thatis, the combination of imaging layer 12 and donor sheet II) may bestored for long periods of time. When ready for use conductive layers 15and 15a are connected through switch 16 thereby placing an electricalfield across the imaging layer 12 whereupon the imaging layer can beexposed to electromagnetic radiation to which it is sensitive.

Referring now to FIG. 2 there is shown an illustrative electricalcircuit provided by the electret of donor sheet II wherein:

' effective charge on imaging layer a, original surface charge onelectret K dielectricconstant of electret d thickness of electret Kdielectric constant of imaging layer d thickness of imaging layer Thepotential available in the electret is utilized to provide theelectrical field across imaging layer 12 via conductive plate I and awhen it is desired. Until such time switch 16 remains open.

FIG. 3 diagrammatically illustrates the electrical field across theimaging layer when switch 16 is closed. Of course, in the manifoldimaging process the electrical field in most cases is applied prior tothe exposure of the imaging layer to actinic electromagnetic radiation.

However, electrically photosensitive materials having fatiguecharacteristics can be employed such that the imaging layer is exposedto actinic electromagnetic radiation prior to the application of theelectric field. The convenience of the imaging member of the presentinvention is equally applicable to either situation. Below is amathematical explanation and description of the electrical field whichcan be effected by means of an electret-donor in accordance with thisinvention.

Symbols employed below which are common with those described aboveretain the same definition.

A V electret A V Imaging Layer e/K o /K (r d /K od /K (rd/K wherein:

AV voltage change across a layer 6,, permittivity of free space Theelectric field in any given imaging layer (E) is determined by theformula:

E o U0 l'/ P)/( 0/ e K50 assuming for an imaging layer:

d/K d,./K,. then E E (T /K6,,

As stated above, one of the advantages of the present invention is theuse of voltages provided by an electret. Electrets can take the form ofathin layer which can be readily made with surface charges in excess ofl0 C/cm Electrets having surface charge densities of from 10 to 10' C/cmare typically useful in this invention and are preferred because theycan provide sufficient potential difference across the imaging layer atthe time of exposure. Such electrets have decay times of greater thanone year for polyester materials and I0 10 years for fluorcarbonmaterials. Thus imaging members in accordance withthis invention can bestored'for long periods of time without ill effect. Further descriptionof such electrets is found in.the publication entitled Electrets andRelated Electrostatic Charge Storage Phenomena" by Lawrence Baxt andMartin Perlman, Copyright 1968 by The Electrochemical Society, lncl, 30E. 42 St., New York, N.Y., which is hereby incorporated by reference. Inthe prior art manifold imaging process, the thickness of an insulatingdonor sheet must be considered when employing electrical field acrossthe imaging layer. That is, higher potentials must be employed withthicker insulating materials in the manifold imaging member. Normallyvoltages in the range are from about l,000 volts per mil of insulatingmaterial up to the electrical breakdown potential of the member istypically found in prior art manifold imaging processes. Such material,of course, refers to the insulating material in the manifold imagingmember or sandwich. For convenience in handling and use in manifoldimaging process, the thickness of a donor sheet in accordance with thisinvention is preferably in the range of from about 0.25 to about 10 milsin thickness. Other thicknesses can be used depending upon the chargedensity of the electret. The electret may comprise wax such as Carnubawax or beeswax. A preferred electret material is Carnuba wax doped withinorganic salts such as an alkali metal halide. Also, Carnuba wax may bedoped with ferric or ferrous chloride Teflon FEP film available from theE. I. DuPont de Nemours and Co. Inc., Wilmington Del. In addition,thermoplastic electrets having sufficient surface charge can be employedand are desirable because of their trans-v parency and durability. Atypical example is Mylar, a polythylene terephthalate availablecommercially from the E. l. DuPont de Nemours Co., Inc., Wilmington,

Del. However, when employed as electret donor sheets 1 of this inventionsuitable protective layers may be required in order that the softmaterial of the electret is not damaged during shipping, storage andhandling of the donor prior to and during its use in the manifoldimaging method. Accordingly, the electret donor sheet may have adheringto its surface opposite the imaging layer a protective layer of moredurable material such as aluminum foil, etc. A particularly preferredprotective layer is a transparent sheet of aluminized Mylar wherein thetransparent aluminum coating is placed adjacent the electret surface. Inuse, the field across the imaging layer is established by placing thealuminum coating in electrical communicationwith a conductive layerresiding on the imaging layer or receiver.

In accordance with this invention, the electret is coated with animaging layer by any suitable means.

such as by a coating knife or wire wound draw down rod. Such coatingtechniques are fully described in the above-mentioned prior art manifoldpatent application and patents.

Referring now to FIGS. 2 and 3, electret 17 may comprise anysuitableelectret material and may be employed in the manifold imagingprocess as the donor sheet. Electrets commonly known in the prior artcan provide a suitable electrical field in the imaging layer. Suchfields across the imaging layer are conveniently in the range of about350 volts per mil and above.

Referring now to FIG. 4 there is shown a process flow diagram of atypical prior art manifold imaging process. Coordinated with FIG. 4 areFIGS. 4a and 4b diagrammatically illustrating a typical manifold imagingmember of this invention being employed in the manifold Such meansdesirably includes switching means26 to permit convenient handling ofthe imaging member during the process. After establishing an electricalfield across the imaging layer the layer is' 'expo'sed to light image29. In the event the electret material is not sufficiently transparentto permit exposure of the imaging layer through it, the imaging layer isthen exposed through a transparent receiver. With the field stillapplied across the manifold sandwich, receiver sheet 22 is separatedfrom donor sheet 21 whereby imaging layer fractures in imagewiseconfiguration providing a negative image on the receiver sheet in'thisparticular illustrative example and a positive image on the donor sheet.

Thus there is provided a manifold imaging method I 1 which obviates theneed for subjecting the manifold imaging member or a part thereof to thehigh voltages at or near the location it is being used. Even in thoseinstances of the prior art wherein the static electrical charges on thesurfaces of one of the donor or receiver sheets were employed to providetheelectrical field across the imaging layer such donor or receiversheet was subjected to high electrical fields at or near the time andplace of the operation of the imaging process. This is required as inmost instances static electrical charges on an insulating member aretransatory and are subject to loss particularly during handling. In thepresent invention the electret isproduced at a time and place remotefrom the operation of the'manifold imaging process. Although a ratherhigh'electrical field is employed to form the electrets such operationisentirely independent from the manifold imaging method. Electrets havethe ability to remain stable for long periods of time, thereby enablinga manifold electret imag-.

ing member readily available at any, time or place needed.

Further in accordance with this invention, an image I transfer processis desirably included whereby the imaging process. The usual procedurein the manifold imaging method is to activate the imaging layer so as torender it structurally fracturable in response to the combined effectsof an electrical field and exposure to electromagnetic radiation towhich it is sensitive. Thus, in FIG. 4a there is shown an activator 18being sprayed from container 19 onto imaging layer 20. Imaging layer 20is residing on electret 21 which together form an electret donor. Aftersuitably activating imaging layer 20 receiver sheet 22, having aconductive surface 23, is placed on the surface of the imaging layer. Inorder to remove excess activator and to insure proper contact with theimaging layer roller 24 traverses receiver 22.

Once the sandwich is formed and the imaging layer is in the suitablystructurally fracturable condition, the electrical field is applied. Asshown in FIG. 4b, the field supplied by the electret donor sheet 21 isapplied across the sandwich by connecting conductive layer 25 underdonor sheet 21 with the conductive layer 23 of receiver sheet 22 bymeans of a conductive wire 24 image produced as shown in FIG. 4b istransferred from either the donor sheet 21 or receiver sheet 22. Themanifold imaging method is uniquely suited for image transfercapability; and several excellent methods of method for transferringimages produced by the manifold imaging process from non-conductivesubstrates, wherein the electrostatic charges remaining from the imagingprocess and residing in the substrate and image are rearranged. Theaforementioned patent and patent applications are hereby incorporated byreference.

Other modifications and ramifications of the present invention willoccur to those skilled in the art upon a reading of the presentdisclosure. Theseare intended to be included within the scope of thisinvention.

What is claimed is:

1. An imaging method which comprises the steps of:

a. providing an imaging member comprising an electret having coatedthereon an electrically photosensitive imaging layer said layer beingstructurally fracturable in response to the combined effects of anapplied electric field and exposure to electromagnetic radiation towhich it is sensitive and residing on said imaging layer a receiversheet;

b. providing a first conductive surface in contact with said electretand a second conductive surface in contact with said receiver sheet andelectrically interconnecting said surfaces whereby an electric field isestablished across said member;

c. exposing said imaging layer to electromagnetic radiation to which itis sensitive;

d. separating said member. while under said field whereby said imaginglayer fractures in imagewise configuration providing a positive image onone of said electret and receiver and a negative image on the other.

2. The process of claim 1 wherein the electret is a thermoplastic resin.

3. The process ofclaim 2 wherein said resin is a polyethyleneterephthalate.

4. The method of claim I wherein said electret has a thickness in therange of from about .25 mils to about mils.

5. The process of claim 2 wherein the electrically photosensitivematerial is an organic material.

6. The method of claim 5 wherein the organic electrically photosensitivematerial is dispersed in an insulating binder.

7. The method of claim 1 wherein the imaging layer comprises anelectrically photosensitive material dispersed in an insulating binder.

8. The process of claim 1 wherein the electret comprises an alkali metaldoped Carnuba wax layer.

9. An imaging member comprising an electrically photosensitive imaginglayer structurally fracturable in response to the combined effects ofelectromagnetic radiation to which it is sensitive and an appliedelectrical field residing upon an electret.

10. The member of claim 9 wherein the electret comprises a thermoplasticresin.

11. The member of claim 10 wherein said resin is a polyethyleneterephthalate.

12. The member of claim 9 wherein the electret has a thickness in therange of from about 0.25 mils to about 10 mils.

13. An imaging member comprising a donor sheet comprising an electrethaving coated thereon an electrically photosensitive imaging layerstructurally fracturable in response to the combined effects of theexposure to electromagnetic radiation to which it is sensitive andapplied electrical field and residing on said imaging layer a receiversheet.

14. The member of claim 13 wherein the electret comprises a polymerselected from the group consisting of Carnuba wax, polycarbonates andflouropolymers.

15. The member of claim 13 wherein the imaging layer comprises anorganic electrically photosensitive material dispersed in a binder.

16. The method of claim 1 further including the step of transferring atleast one of said images to another substrate.

17. The method of claim 16 wherein said transfer is accomplished by theapplication of pressure to said sheet and substrate.

18. The method of claim 16 wherein said transfer is accomplished byrearrangement of electrostatic charges remaining in said sheet and imagefrom said imaging process.

1. AN IMAGING METHOD WHICH COMPRISES THE STEPS OF: A. PROVIDING ANIMAGING MEMBER COMPRISING AN ELECTRET HAVING COATED THEREON ANELECTRICALLY PHOTOSENSITIVE IMAGING LAYER SAID LAYER BEING STRUCTURALLYFRACTURABLE IN RESPONSE TO THE COMBINED EFFECTS OF AN APPLIED ELECTRICFIELD AND EXPOSURE TO ELECTROMAGNETIC RADIATION TO WHICH IT IS SENSITIVEAND RESIDING ON SAID IMAGING LAYER A RECEIVER SHEET; B. PROVIDING AFIRST CONDUCTIVE SURFACE IN CONTACT WITH SAID ELECTRET AND A SECONDCONDUCTIVE SURFACE IN CONTACT WITH SAID RECEIVER SHEET AND ELECTRICALLYINTERCONNECTING SAID SURFACES WHEREBY AN ELECTRIC FIELD IS ESTABLISHEDACROSS SAID MEMBER; C. EXPOSING SAID IMAGING LAYER TO ELECTROMAGNETICRADIATION TO WHICH IT IS SENSITIVE; D. SEPARATING SAID MEMBER WHILEUNDER SAID FIELD WHEREBY SAID IMAGING LAYER FRACTURES IN IMAGEWISECONFIGURATION PROVIDING A POSITIVE IMAGE ON ONE OF SAID ELECTRET ANDRECEIVER AND A NEGATIVE IMAGE ON THE OTHER.
 2. The process of claim 1wherein the electret is a thermoplastic resin.
 3. The process of claim 2wherein said resin is a polyethylene terephthalate.
 4. The method ofclaim 1 wherein said electret has a thickness in the range of from about.25 mils to about 10 mils.
 5. The process of claim 2 wherein theelectrically photosensitive material is an organic material.
 6. Themethod of claim 5 wherein the organic electrically photosensitivematerial is dispersed in an insulating binder.
 7. The method of claim 1wherein the imaging layer comprises an electrically photosensitivematerial dispersed in an insulating binder.
 8. The process of claim 1wherein the electret comprises an alkali metal doped Carnuba wax layer.9. An imaging member comprisiNg an electrically photosensitive imaginglayer structurally fracturable in response to the combined effects ofelectromagnetic radiation to which it is sensitive and an appliedelectrical field residing upon an electret.
 10. The member of claim 9wherein the electret comprises a thermoplastic resin.
 11. The member ofclaim 10 wherein said resin is a polyethylene terephthalate.
 12. Themember of claim 9 wherein the electret has a thickness in the range offrom about 0.25 mils to about 10 mils.
 13. An imaging member comprisinga donor sheet comprising an electret having coated thereon anelectrically photosensitive imaging layer structurally fracturable inresponse to the combined effects of the exposure to electromagneticradiation to which it is sensitive and applied electrical field andresiding on said imaging layer a receiver sheet.
 14. The member of claim13 wherein the electret comprises a polymer selected from the groupconsisting of Carnuba wax, polycarbonates and flouropolymers.
 15. Themember of claim 13 wherein the imaging layer comprises an organicelectrically photosensitive material dispersed in a binder.
 16. Themethod of claim 1 further including the step of transferring at leastone of said images to another substrate.
 17. The method of claim 16wherein said transfer is accomplished by the application of pressure tosaid sheet and substrate.
 18. The method of claim 16 wherein saidtransfer is accomplished by rearrangement of electrostatic chargesremaining in said sheet and image from said imaging process.